In-situ post-deposition oxidation treatment for improved magnetic recording media

ABSTRACT

A method of manufacturing a magnetic recording medium comprises sequential steps of:  
     (a) providing an apparatus for manufacturing the medium;  
     (b) supplying the apparatus with a substrate for the medium;  
     (c) forming a magnetic recording layer on the substrate in a first portion of the apparatus;  
     (d) treating the magnetic recording layer with oxygen gas in a second portion of the apparatus at a sub-atmospheric pressure and for an interval sufficient to provide the resultant medium with at least one of the following, relative to a similar medium manufactured by a similar method but wherein the oxygen treatment of step (d) is not performed:  
     (i) a more negative nucleation field (H n );  
     (ii) increased remanent squareness (S r );  
     (iii) increased signal-to-medium noise ratio (SMNR);  
     (iv) narrower switching field distribution (SFD); and  
     (v) decreased thermal decay rate; and  
     (e) forming a protective overcoat layer on the oxygen-treated magnetic recording layer in a third portion of the apparatus.

CROSS-REFERENCE TO PROVISIONAL APPLICATION

[0001] This application claims priority from U.S. provisional patentapplication Serial No. 60/475,834 filed Jun. 3, 2003, the entiredisclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a method for improving theperformance characteristics of high areal recording density magneticmedia, and to improved media obtained thereby which exhibit increasednegative nucleation fields, remanent squareness, and signal-to-mediumnoise ratios, decreased thermal decay rate, and narrower switching fielddistribution (“SFD”). The invention is of particular utility in themanufacture of high areal recording density perpendicular magnetic mediain the form of hard disks.

BACKGROUND OF THE INVENTION

[0003] Magnetic media are widely used in various applications,particularly in the computer industry, and efforts are continually madewith the aim of increasing the areal recording density, i.e., bitdensity of the magnetic media. In this regard, so-called “perpendicular”recording media have been found to be superior to the more conventional“longitudinal” media in achieving very high bit densities. Inperpendicular magnetic recording media, residual magnetization is formedin a direction perpendicular to the surface of the magnetic medium,typically a layer of a magnetic material on a suitable substrate. Veryhigh linear recording densities are obtainable by utilizing a“single-pole” magnetic transducer or “head” with such perpendicularmagnetic media.

[0004] Efficient, high bit density recording utilizing a perpendicularmagnetic medium requires interposition of a relatively thick (ascompared with the magnetic recording layer), magnetically “soft”underlayer (“SUL”) layer, i.e., a magnetic layer having a relatively lowcoercivity of about 1 kOe or below, such as of a NiFe alloy (Permalloy),between the non-magnetic substrate, e.g., of glass, aluminum (Al) or anAl-based alloy, and the magnetically “hard” recording layer havingrelatively high coercivity of several kOe, typically about 3-6 kOe,e.g., of a cobalt-based alloy (e.g., a Co—Cr alloy such as CoCrPtB)having perpendicular anisotropy. The magnetically soft underlayer servesto guide magnetic flux emanating from the head through the hard,perpendicular magnetic recording layer.

[0005] A typical conventional perpendicular recording system 10utilizing a vertically oriented magnetic medium 1 with a relativelythick soft magnetic underlayer, a relatively thin hard magneticrecording layer, and a single-pole head, is illustrated in FIG. 1,wherein reference numerals 2, 2A, 3, 4, and 5, respectively, indicate anon-magnetic substrate, an adhesion layer (optional), a soft magneticunderlayer, at least one non-magnetic interlayer, and at least oneperpendicular hard magnetic recording layer. Reference numerals 7 and 8,respectively, indicate the single and auxiliary poles of a single-polemagnetic transducer head 6. The relatively thin interlayer 4 (alsoreferred to as an “intermediate” layer), comprised of one or more layersof non-magnetic materials, serves to (1) prevent magnetic interactionbetween the soft underlayer 3 and the at least one hard recording layer5 and (2) promote desired microstructural and magnetic properties of theat least one hard recording layer.

[0006] As shown by the arrows in the figure indicating the path of themagnetic flux φ, flux φ is seen as emanating from single pole 7 ofsingle-pole magnetic transducer head 6, entering and passing through theat least one vertically oriented, hard magnetic recording layer 5 in theregion above single pole 7. entering and travelling along soft magneticunderlayer 3 for a distance, and then exiting therefrom and passingthrough the at least one perpendicular hard magnetic recording layer 5in the region above auxiliary pole 8 of single-pole magnetic transducerhead 6. The direction of movement of perpendicular magnetic medium 1past transducer head 6 is indicated in the figure by the arrow abovemedium 1.

[0007] With continued reference to FIG. 1, vertical lines 9 indicategrain boundaries of polycrystalline layers 4 and 5 of the layer stackconstituting medium 1. Since magnetically hard main recording layer 5 isepitaxially formed on interlayer 4, the grains of each polycrystallinelayer are of substantially the same width (as measured in a horizontaldirection) and in vertical registry (i.e., vertically “correlated” oraligned). Completing the layer stack is a protective overcoat layer 11,such as of a diamond-like carbon (DLC), formed over hard magnetic layer5, and a lubricant topcoat layer 12, such as of a perfluoropolyethylenematerial, formed over the protective overcoat layer.

[0008] Substrate 2 is typically disk-shaped and comprised of anon-magnetic metal or alloy, e.g., Al or an Al-based alloy, such asAl—Mg having an Ni—P plating layer on the deposition surface thereof, orsubstrate 2 is comprised of a suitable glass, ceramic, glass-ceramic,polymeric material, or a composite or laminate of these materials;optional adhesion layer 2A, if present, may comprise an up to about 30 Åthick layer of a material such as Ti or a Ti alloy; soft magneticunderlayer 3 is typically comprised of an about 500 to about 4,000 Åthick layer of a soft magnetic material selected from the groupconsisting of Ni, NiFe (Permalloy), Co, CoZr, CoZrCr, CoZrNb, CoFeZrNb,CoFe, Fe, FeN, FeSiAl, FeSiAlN, FeCoB, FeCoC, etc.; interlayer 4typically comprises an up to about 300 Å thick layer or layers ofnon-magnetic material(s), such as Ru, TiCr, Ru/CoCr₃₇Pt₆, RuCr/CoCrPt,etc.; and the at least one hard magnetic layer 5 is typically comprisedof an about 100 to about 250 Å thick layer(s) of Co-based alloy(s)including one or more elements selected from the group consisting of Cr,Fe, Ta, Ni, Mo, Pt, V, Nb, Ge, B, and Pd, iron nitrides or oxides, or a(CoX/Pd or Pt)_(n) multilayer magnetic superlattice structure, where nis an integer from about 10 to about 25, each of the alternating, thinlayers of Co-based magnetic alloy is from about 2 to about 3.5 Å thick,X is an element selected from the group consisting of Cr, Ta, B, Mo, Pt,W, and Fe, and each of the alternating thin, non-magnetic layers of Pdor Pt is up to about 10 Å thick. Each type of hard magnetic recordinglayer material has perpendicular anisotropy arising frommagneto-crystalline anisotropy (1^(st) type) and/or interfacialanisotropy (2^(nd) type).

[0009] Another way of classifying perpendicular magnetic recording mediainto different types is based on the media properties provided by thematerial(s) utilized for the magnetically hard recording layer(s) 5. Forexample, as indicated above, the at least one magnetically hard,perpendicular recording layer 5 can comprise magnetic alloys which aretypically employed in longitudinal media, e.g., CoCr alloys, ormulti-layer magnetic superlattice structures, such as the aforementioned(CoX/Pd or Pt)_(n) superlattice structures. Referring to FIG. 2 (A),graphically shown therein is an idealized representation of a Kerrhysteresis loop of a perpendicular magnetic recording medium, whereinthe nucleation field (H_(n)), coercivity (H_(c)), and saturation field(H_(sat)) are defined. H_(n) is defined as negative (−) when located inthe second (i.e., upper left) quadrant of the graph and as positive (+)when located in the first (i.e., upper right) quadrant. RepresentativeM-H hysteresis loops of magnetic recording layers comprised of thesedifferent types of materials are shown in FIG. 2(B)-2(C).

[0010] As is evident from FIG. 2(B) showing the M-H loop of aperpendicular recording medium comprising a CoCr alloy, such type mediatypically exhibit a relatively low coercivity, low remanent squareness,i.e., less than 1, and a positive nucleation field H_(n). In addition,the occurrence of magnetic domain reversal within bits, caused by thepresence of high demagnetization fields in CoCr-based perpendicularrecording media, is problematic with such media in that the phenomenonis a significant source of media noise reducing the SMNR. A highremanent squareness and a negative nucleation field H_(n) are requiredin order to obtain good bit stability.

[0011] By contrast, and as evidenced by FIG. 2(C) showing the M-H loopof a perpendicular recording medium comprising a (CoX/Pd)_(n) multilayermagnetic superlattice structure, such type media advantageously exhibita relatively high coercivity, remanent squareness of about 1, and anegative nucleation field H_(n), which characteristics are attributed tothe high anisotropy energy of such type media arising from interfacialanisotropy effects. However, the grains of the multilayer magneticsuperlattice structure tend to experience exchange coupling leading totransition noise. Moreover, notwithstanding the possibility of furtherimprovements in multilayer magnetic superlattice structures for use inthe fabrication of high recording density magnetic media, significantcurrent issues/problems remain pertaining to the ability to manufacturesuch structures in a commercially viable manner.

[0012] It is believed that high areal recording densities of about 200Gbit/in² or greater are possible with perpendicular magnetic mediautilizing CoCr-based magnetic alloys as the magnetically hard recordinglayer. However, the obtainment of such high areal recording densitiesrequires CoCr-based perpendicular media which exhibit the advantageousproperties associated with multilayer magnetic superlattice-based media,i.e., high coercivity, remanent squareness of about 1, and a negativenucleation field H_(n).

[0013] In general, ultra-high areal density perpendicular magneticrecording media require perpendicular magnetic recording layers withhigh perpendicular anisotropy (K_(u)) and correspondingly high values ofcoercivity (H_(c)) and nucleation field (H_(n)), which high values arenecessary for providing the media with resistance to the largedemagnetization effects from the perpendicular recordinggeometry/system, for maintaining thermal stability with the very smallgrain sizes (volumes) required for ultra-high areal density recording,and to avoid erasure of the magnetization pattern by the auxiliary pole8 of the single-pole transducer head 6.

[0014] A significant noise source in Co-alloy based perpendicularmagnetic recording media is reversed magnetic domains within bits, whichreversal is caused by high demagnetization fields within the co-basedalloy. As a consequence, high remanent squareness (“S_(r)”) and, asexplained above, a negative nucleation field (H_(n)) are required forobtaining good bit stability. The higher values of perpendicularanisotropy (K_(u)) necessary for obtaining good thermal stability aretraditionally obtained by increasing the Pt content of the bulk Co-basedmagnetic alloy. However, such increase in the Pt contentdisadvantageously decreases the amount of key segregating elements thatcan be included in the bulk Co-based alloy and degrades thesignal-to-media noise ratio (SMNR) of the media.

[0015] In view of the above, there exists a clear need for an improvedhigh areal recording density, magnetic information/data recording,storage, and retrieval media, e.g., perpendicular media, including Coalloy-based magnetically hard recording layers which exhibitsubstantially increased signal-to-media noise ratios (SMNR), highcoercivity, remanent squareness of about 1, and a negative nucleationfield H_(n). In addition, there exists a need for an improved method formanufacturing high areal recording density, magnetic recording media,e.g., perpendicular media, employing Co alloy-based magnetically hardrecording layers, which media exhibit substantially increasedsignal-to-media noise ratio (SMNR), high coercivity (H_(c)), remanentsquareness (S_(r)) of about 1, a negative nucleation field (H_(n)), anarrow switching field distribution (SFD), and can be readily andeconomically fabricated by means of conventional continuousmanufacturing techniques and instrumentalities.

[0016] The present invention addresses and solves problems attendantupon the use of Co alloy-based magnetically hard recording layers in themanufacture of high bit density magnetic media such as perpendicularmedia, which problems include, inter alia, noise generation whichadversely affects the SMNR of the media, while maintaining allstructural and mechanical aspects of high bit density recordingtechnology. Moreover, the magnetic media of the present invention can befabricated by means of conventional manufacturing techniques, e.g.,sputtering.

DISCLOSURE OF THE INVENTION

[0017] An advantage of the present invention is an improved method formanufacturing a magnetic recording medium.

[0018] Another advantage of the present invention is improvedperpendicular magnetic recording media manufactured by the improvedmethod of the invention.

[0019] Yet another advantage of the present invention is an improveddisk drive comprising an improved perpendicular magnetic recordingmedium manufactured by the improved method of the invention.

[0020] Still another advantage of the present invention is an improvedmethod of manufacturing magnetic recording media according to acontinuous process.

[0021] Additional advantages and other features of the present inventionwill be set forth in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from the practice of thepresent invention. The advantages of the present invention may berealized and obtained as particularly pointed out in the appendedclaims.

[0022] According to an aspect of the present invention, the foregoingand other advantages are obtained in part by a method of manufacturing amagnetic recording medium, comprising sequential steps of:

[0023] (a) providing an apparatus for manufacturing the medium;

[0024] (b) supplying said apparatus with a substrate for the medium;

[0025] (c) forming a magnetic recording layer on the substrate in afirst portion of the apparatus;

[0026] (d) treating the magnetic recording layer with oxygen gas in asecond portion of the apparatus at a sub-atmospheric pressure and for aninterval sufficient to provide the resultant medium with at least one ofthe following, relative to a similar medium manufactured by a similarmethod but wherein the oxygen treatment of step (d) is not performed:

[0027] (i) a more negative nucleation field (H_(n));

[0028] (ii) increased remanent squareness (S_(r));

[0029] (iii) increased signal-to-medium noise ratio (SMNR);

[0030] (iv) narrower switching field distribution (SFD); and

[0031] (v) decreased thermal decay rate; and

[0032] (e) forming a protective overcoat layer on the oxygen-treatedmagnetic recording layer in a third portion of the apparatus.

[0033] According to embodiments of the present invention, step (a)comprises providing an apparatus including at least said first, second,and third spaced-apart portions; the apparatus is adapted for continuousmanufacture of a plurality of media and includes means for transportingthe substrate serially through the first, second, and third spaced-apartportions; the first, second, and third spaced-apart, serially arrangedportions of the apparatus respectively comprise first, second, and thirdspaced-apart chambers and at least the second chamber is adapted forproviding a sub-atmospheric pressure therein; the second chambercomprises means for flowing a mixture of oxygen gas diluted with aninert carrier gas past a surface of the magnetic recording layer formedon the substrate in step (c); and the first and third chambers of theapparatus are adapted for performing a thin film deposition processtherein, e.g., at least the first chamber of the apparatus is adaptedfor performing a sputtering process therein.

[0034] Preferred embodiments of the invention include those wherein step(c) comprises forming a magnetic recording layer selected from the groupconsisting of: (1) a Co-based alloy, Cr-rich (i.e., Cr-segregated) grainboundary type magnetic layer; (2) a granular-type magnetic layer; (3) asuperlattice-type layer; and (4) an L1₀ ferromagnetic metal alloy-typelayer.

[0035] According to a particular embodiment of the invention, step (c)comprises forming a Co-based alloy, Cr-rich (i.e., Cr-segregated) grainboundary-type magnetic recording layer comprised of a CoCrPtX alloy,where X=at least one element selected from the group consisting of Ta,B, Mo, V, Nb, W, Zr, Re, Ru, Cu, Ag, Hf, Ir, and Y, whereinCo-containing grains with hcp lattice structure are segregated byCr-rich grain boundaries; step (d) comprises treating the magneticrecording layer with a gas mixture comprising up to about 20% oxygen gasin at least one inert diluent gas, at a total gas pressure up to about50 mTorr, and for an interval up to about 10 sec.; and step (c) furthercomprises use of a heated substrate during formation of the magneticrecording layer to effect segregation of Cr in the grain boundaries.

[0036] In accordance with another particular embodiment of the presentinvention, step (c) comprises forming a granular-type magnetic recordinglayer comprised of a CoPtX alloy, where X=at least one material selectedfrom the group consisting of Cr, Ta, B, Mo, V, Nb, W, Zr, Re, Ru, Cu,Ag, Hf, Ir, Y, SiO₂, SiO, Si₃N₄, Al₂O₃, AlN, TiO, TiO₂, TiO_(x), TiN,TiC, Ta₂O₃, NiO, and CoO, and wherein Co-containing grains with hcplattice structure are segregated by oxide, nitride, or carbide grainboundaries; step (d) comprises treating the magnetic recording layerwith a gas mixture comprising up to about 20% oxygen gas in at least oneinert diluent gas, at a total gas pressure up to about 50 mTorr, and foran interval up to about 10 sec.; and step (d) comprises treating themagnetic recording layer with oxygen gas without applying heat thereto.

[0037] According to still another particular embodiment of the presentinvention, step (c) comprises forming a superlattice-type magneticrecording layer comprising a multi-layer (CoX/Pd)_(n) or (CoX/Pt)_(n)structure, where n is an integer from about 10 to about 25 and X is anelement selected from the group consisting of Cr, Ta, B, Mo, Pt. W, andFe; and step (d) comprises treating the magnetic recording layer withoxygen gas without applying heat thereto.

[0038] In accordance with yet another particular embodiment of theinvention, step (c) comprises forming an L1₀ ferromagnetic metalalloy-type layer comprising a FePt or CoPt alloy.

[0039] Additional preferred embodiments of the invention include thosewherein step (b) comprises supplying the apparatus with a disk-shapedsubstrate for a hard disk magnetic recording medium; and wherein step(e) comprises forming a carbon-based protective overcoat layer on theoxygen-treated magnetic recording layer.

[0040] According to other aspects of the present invention, improvedperpendicular magnetic recording media manufactured according to theabove-described embodiments and disk drives comprising same areprovided.

[0041] Still another aspect of the present invention is a method ofmanufacturing magnetic recording media according to a continuousprocess, comprising sequential steps of:

[0042] (a) providing at least one substrate for the magnetic recordingmedia;

[0043] (b) providing an apparatus adapted for continuous manufacturingof the magnetic recording media, comprising at least first, second, andthird spaced-apart, serially arranged processing chambers and includingmeans for transporting the at least one substrate serially through atleast the first, second, and third spaced-apart processing chambers;

[0044] (c) transporting the substrate through the first processingchamber while forming a magnetic recording layer thereon;

[0045] (d) transporting the substrate with the magnetic recording layerformed thereon to the second processing chamber;

[0046] (e) transporting the substrate through the second processingchamber while treating the magnetic recording layer with oxygen gas at asub-atmospheric pressure and for an interval sufficient to provide theresultant media with at least one of the following, relative to similarmedia manufactured by a similar method but wherein the oxygen treatmentof step (e) is not performed:

[0047] (i) a more negative nucleation field (H_(n));

[0048] (ii) increased remanent squareness (S_(r));

[0049] (iii) increased signal-to-medium noise ratio (SMNR);

[0050] (iv) narrower switching field distribution (SFD); and

[0051] (v) decreased thermal decay rate;

[0052] (f) transporting the substrate with the oxygen-treated magneticrecording layer formed thereon to the third processing chamber; and

[0053] (g) transporting the substrate through the third processingchamber while forming a protective overcoat layer on the oxygen-treatedmagnetic recording layer; wherein:

[0054] the substrate is transported between and through each of thefirst, second, and third processing chambers at a substantially constantrate.

[0055] According to preferred embodiments of the present invention, step(a) comprises providing at least one disk-shaped substrate for hard diskmagnetic recording media; step (b) comprises providing an apparatuswherein the first and third chambers are adapted for performing a thinfilm deposition process therein and at least the second chamber isadapted for providing a sub-atmospheric pressure therein; and step (c)comprises forming a magnetic recording layer selected from the groupconsisting of: (1) a Co-based alloy, Cr-rich (i.e., Cr-segregated) grainboundary-type magnetic layer; (2) a granular-type magnetic layer; (3) asuperlattice-type layer; and (4) an L1₀ ferromagnetic metal alloy-typelayer.

[0056] Additional advantages and aspects of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein embodiments of the present invention areshown and described, simply by way of illustration of the best modecontemplated for practicing the present invention. As will be described,the present invention is capable of other and different embodiments, andits several details are susceptible of modification in various obviousrespects, all without departing from the spirit of the presentinvention. Accordingly, the drawings and description are to be regardedas illustrative in nature, and not as limitative.

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The following detailed description of the embodiments of thepresent invention can best be understood when read in conjunction withthe following drawings, in which the various features are notnecessarily drawn to scale but rather are drawn as to best illustratethe pertinent features, wherein:

[0058]FIG. 1 schematically illustrates, in simplified, cross-sectionalview, a portion of a magnetic recording, storage, and retrieval systemcomprised of a conventional perpendicular-type magnetic recording mediumincluding a soft magnetic underlayer, and a single-pole transducer head;

[0059]FIG. 2(A) is an idealized graphical representation of a Kerr M-Hhysteresis loop of a perpendicular magnetic recording medium;

[0060] FIGS. 2(B) and 2(C), respectively, are graphical representationsof Kerr M-H hysteresis loops of perpendicular magnetic recording mediaexhibiting positive and negative nucleation fields (H_(n));

[0061] FIGS. 3(A) and 3(B) are graphs for illustrating the variation ofcoercivity (H_(c)) and nucleation field (H_(n)) of CoCrPt-based, Cr-rich(i.e., Cr-segregated) grain boundary type perpendicular magneticrecording media, fabricated in a sputtering apparatus, as a function of% oxygen content during in situ post-deposition oxidation treatment ofthe magnetic recording layer according to an embodiment of the presentinvention;

[0062]FIG. 4 is a graphical representation of the Kerr M-H hysteresisloops of samples of the perpendicular magnetic recording media of FIG.3(B);

[0063] FIGS. 5(A) and 5(B) are graphs for illustrating thesignal-to-media noise ratios (SMNR) and % thermal decay rates ofCoCrPt-based, Cr-rich (i.e., Cr-segregated) grain boundary typeperpendicular magnetic recording media fabricated with and without thein situ post-deposition oxidation treatment of the magnetic recordinglayer according to the present invention;

[0064]FIG. 6 is a graph for illustrating the variation of coercivity(H_(c)) and nucleation field (H_(n)) of CoCrPt-based, Cr-rich (i.e.,Cr-segregated) grain boundary type perpendicular magnetic recordingmedia as a function of very low % oxygen contents during in situpost-deposition oxidation treatment of the magnetic recording layeraccording to the present invention;

[0065]FIG. 7 is a graphical representation of the Kerr M-H hysteresisloops of samples of the perpendicular magnetic recording media of FIG.6;

[0066]FIG. 8 is a graph for illustrating the variation of coercivity(H_(c)) and nucleation field (H_(n)) of CoCrPt-based, Cr-rich (i.e.,Cr-segregated) grain boundary type perpendicular magnetic recordingmedia, fabricated in a different sputtering apparatus, as a function of% oxygen content during in situ post-deposition oxidation treatment ofthe magnetic recording layer according to another embodiment of thepresent invention;

[0067] FIGS. 9(A) and 9(B), respectively, are graphs for illustratingthe variation of signal-to-noise ratio (SNR) and coercivity(H_(c))+nucleation field (H_(n)) of (CoPt₁₈)O_(x) granular-typeperpendicular magnetic recording media as a function of % oxygen contentduring in situ post-deposition oxidation treatment of the magneticrecording layer according to a further embodiment the present invention;and

[0068] FIGS. 10(A) and 10(B), respectively, are graphs for illustratingthe variation of signal-to-noise ratio (SNR) and coercivity(H_(c))+nucleation field (H_(n)) of CoCr₆Pt₁₈(SiO₂)₄O_(x) granular-typeperpendicular magnetic recording media as a function of % oxygen contentduring in situ post-deposition oxidation treatment of the magneticrecording layer according to a still further embodiment of the presentinvention.

DESCRIPTION OF THE INVENTION

[0069] The present invention is based upon recognition by the inventorsthat high areal density magnetic recording media, such as perpendicularmedia, can be readily and reliably fabricated with significantlyimproved recording performance parameters by performing an in situpost-deposition treatment of the magnetic recording layer with oxygengas, i.e., immediately subsequent to formation thereof and just prior toformation of a protective overcoat layer thereon. Specifically, the insitu post-deposition oxygen treatment of the magnetic recording layerprovided by the present invention affords a number of improvements inmedia performance, relative to similar media prepared without theinventive oxygen post-treatment of the magnetic recording layer,including at least one of: a more negative nucleation field (H_(n)); anincreased remanent squareness (S_(r)); an increased signal-to-mediumnoise ratio (SMNR); a narrower switching field distribution (SFD); and adecreased thermal decay rate.

[0070] According to advantageous features of the invention, the in situpost-deposition treatment of the magnetic recording layer with oxygengas is performed at a sub-atmospheric pressure with a low concentrationof oxygen gas carried in an inert diluent gas, and in a dedicated spaceor chamber located intermediate a pair of spaces or chambersrespectively dedicated for formation of the magnetic recording andprotective overcoat layers. According to further advantageous featuresof the instant invention, the in situ post-deposition treatment of themagnetic recording layer with oxygen gas is performed rapidly, at ratesconsistent with, thus facilitating use of, continuously operatedapparatus utilized for high product throughput, cost-effective,automated manufacture of magnetic recording media, e.g., in-line,multi-chamber sputtering apparatus.

[0071] As indicated supra, high areal recording density magnetic media,e.g., perpendicular media, require magnetic recording layers exhibitinghigh perpendicular anisotropy (K_(u)) and correspondingly highcoercivity (H_(c)) and nucleation field (H_(n)). The high values ofH_(c) and H_(n) are necessary in order to resist the largedemagnetization effects inherent in the design/geometry of theperpendicular recording media and systems, to maintain good thermalstability in face of the ever smaller grain volumes associated with suchhigh areal recording density media, and to avoid bit erasure by theauxiliary magnetic pole of the read/write transducer head. In addition,reversal of magnetic domains within bits, caused by the highdemagnetization fields in Co alloy-based (segregation-type)perpendicular media have been determined to be a significant source ofmedia noise. High remanent squareness (S_(r)) and a negative nucleationfield (H_(n)) are required for maintaining good bit stability. On theother hand, the higher values of perpendicular anisotropy (K_(u))required for thermal stability are traditionally obtained by increasingthe Pt content of the bulk CoCrPt magnetic alloy. However, this approachdisadvantageously decreases the amount of key segregating elements thatcan be included in the bulk alloy and therefore results in degradationof the signal-to-medium noise ratio (SMNR).

[0072] As a consequence of the above, a desirable goal is to enableformation of high areal density magnetic recording media, e.g.,perpendicular media, with a sufficiently negative nucleation field(H_(n)) and remanent squareness (S_(r)) substantially equal to 1,without incurring degradation of the SMNR. An approach for meeting theabove-mentioned goal, according to the present invention, is in situpost-deposition treatment of the just-deposited magnetic recording layerwith oxygen gas, prior to formation of a protective overcoat layerthereon.

[0073] According to an advantageous feature of the instant invention,the in situ post-deposition treatment of the just-deposited magneticrecording layer with oxygen gas may form part of a continuous, highproduct throughput, automated manufacturing process for magneticrecording media utilizing conventional in-line or circularly arrangedmulti-chamber apparatus, e.g., sputtering apparatus. More specifically,according to the invention, the in situ post-deposition treatment of thejust-deposited magnetic recording layer with oxygen gas may be performedby exposing the media substrate with the just-formed magnetic recordingthereon to a flow or stream of a sub-atmospheric pressure gas comprisedof a relatively small amount of oxygen gas in admixture with arelatively large amount of at least one inert diluent or carrier gas,e.g., argon and/or nitrogen, the treatment being performed in adedicated process station located between a pair of process stationsrespectively dedicated for depositing the magnetic recording andprotective overcoat layers on the media substrate. The in situpost-deposition treatment of the just-deposited magnetic recording layerwith oxygen gas may be rapidly performed within the dedicated processstation, at media substrate transport rates consistent with thesubstrate transport rates between and through the other process stationsof the continuously operated apparatus.

[0074] According to the invention, the magnitude and direction of thechanges in coercivity (H_(c)) and nucleation field (H_(n)) depend uponthe design parameters of the media, e.g., magnetic alloy composition andthickness of the recording layer. The optimum amount of oxygen in thegas mixture utilized for the in situ post-deposition treatment alsodepends upon the manner by which the gas mixture is introduced andflowed through the dedicated process station and the efficiency of gasremoval therefrom. The in situ post-deposition treatment with oxygen ofthe present invention can form part of the fabrication process of alltypes of magnetic recording media requiring magnetic recording layerswith well-defined grains, e.g., segregated grains. Such recording layersinclude, inter alia, (1) Co-based alloy, Cr-rich (i.e., Cr-segregated)grain boundary type magnetic layers (e.g., traditional hcp-structured,CoCr based-alloy layers); (2) granular-type magnetic layers (i.e., wherethe grains are separated by oxides, nitrides, or carbides, e.g.,reactively sputtered CoO_(x) alloy-based layers); (3) asuperlattice-type layer (e.g., (Co/Pd or Pt)_(n) multi-layers); and (4)L1₀ ferromagnetic metal alloy-type layers (e.g., FePt or CoPtalloy-based layers). Since a high sputtering pressure is required forforming more porous granular and multi-layer type magnetic recordinglayers, it is relatively easy for oxygen atoms supplied thereto duringthe in situ post-deposition treatment to migrate into the grainboundaries and effect better decoupling between adjacent grains thanwith the other enumerated types of magnetic recording layers. As aconsequence, use of heated substrates during the in situ post-depositiontreatment with oxygen gas is generally not required with thegranular-type magnetic recording layers, whereas heated substrates may,if desired, be utilized during in situ post-deposition treatment of theother types of magnetic recording layers with oxygen gas.

[0075] The versatility of the present invention will now be demonstratedby reference to the following examples.

[0076] Perpendicular media with Co-based alloy, Cr-rich (Cr-segregated)grain boundary type magnetic recording layers—A multi-chamber,single-disk type sputtering apparatus was utilized for fabricatingmagnetic recording media comprising Co-based alloy, Cr-rich(Cr-segregated) grain boundary type magnetic recording layers, whereinthe mixture of oxygen gas and inert carrier (or diluent) gas entered thededicated in situ post-deposition treatment chamber via the top thereofand residual gas was withdrawn via the bottom.

[0077] As indicated above, such Co-based alloy, Cr-rich (i.e.,Cr-segregated) grain boundary type magnetic recording layers typicallycomprise CoCrPtX alloys, where X is at least one element selected fromTa, B, Mo, V, Nb, W, Zr, Re, Ru, Ag, Hf, Ir, and Y, and whereinCo-containing grains with hcp lattice structure are segregated byCr-rich grain boundaries.

[0078] The following media structures were formed:

Substrate//adhesion layer//soft magneticunderlayer/interlayer(s)//recording layer(s)//protective overcoat layer

[0079] wherein:

[0080] adhesion layer=Ti

[0081] soft magnetic underlayer=FeCoB

[0082] interlayer(s)=Ru/CoCrPt or RuCr₁₀/CoCrPt

[0083] recording layer(s)=CoCrPtB/CoCrPt

[0084] protective overcoat layer=carbon (C)-based

[0085] The target compositions for the various sputtered layers were asfollows:

[0086] interlayer: CoCr₃₇Pt₆

[0087] recording layer(s): CoCr₂₂Pt₁₉B₁ and CoCr₂₀Pt₁₇.

[0088] The Ti adhesion layer, Ru/CoCrPt or RuCr₁₀/CoCrPt interlayers,and the CoCrPtB and CoCrPt recording layers were sputtered in an Aratmosphere at about 6 mTorr. The FeCoB soft magnetic underlayer wassputtered in an Ar atmosphere at about 2 MTorr. The substrate was heatedbetween sputtering of the Ru or RuCr₁₀ and the CoCrPt interlayers tofacilitate Cr segregation in the recording layer(s) subsequently formedthereover. The % content of oxygen (O₂) gas in the oxygen/Ar inertcarrier or diluent gas mixture introduced into the dedicated in situpost-deposition treatment chamber positioned between the recording layerand protective overcoat deposition chambers was varied so as to exposedisks transported therethrough to different amounts of oxygen. The flowof oxygen was controlled by a pair of Mass Flow Controllers (MFC),wherein the flow of pure Ar gas was controlled by MFC 1 and the flow ofan O₂/Ar gas mixture was controlled by MFC 2. Finer adjustment of the O₂content of the treatment gas was accomplished by attaching a lower O₂content gas cylinder to MFC 2. The gas flows utilized for each datapoint in the graphs of the drawing figures are indicated in Table I, andthe total gas pressure was less than about 20 mTorr, i.e., about 13mTorr. TABLE I % O₂ Content in O₂/Ar 0 2 4 6 8 10 MFC 1: 100% Ar (sccm)40 36 32 28 24 20 MFC 2: 20% O₂ in Ar 0 4 8 12 16 20 (sccm) % O₂ Contentin O₂/Ar 0 0.1 0.2 0.3 0.4 0.5 MFC 1: 100% Ar (sccm) 40 36 32 28 24 20MFC 2: 1% O₂ in Ar (sccm) 0 4 8 12 16 20 % O₂ Content in O₂/Ar 0 0.020.04 0.06 0.08 0.10 MFC 1: 100% Ar (sccm) 40 32 24 16 8 0 MFC 2: 0.1% O₂in Ar 0 8 16 24 32 40 (sccm)

[0089] When the O₂ content was increased from 0 to about 10%, thecoercivity (H_(c)) and nucleation field (H_(n)) of media of layerstructure: substrate//adhesion layer: Ti (3 nm)//soft magneticunderlayer: FeCoB (160 nm)//interlayer(s): Ru (2 nm)/CoCr₃₇Pt₆ (7.5nm)//recording layer(s): CoCr₂₂Pt₁₉B₁ (3 nm)CoCr₂₀Pt₁₇ (8.5 nm) varied,as graphically illustrated in FIG. 3(A). As is apparent from the figure,the nucleation field (H_(n)) increases dramatically as the media isexposed to post treatment gases containing 2% or more O₂ in Ar, whilethe coercivity (H_(c)) is relatively unaffected. FIG. 3(B) graphicallyillustrates the changes in H_(c) and H_(n) of similar media, but whereinthe thickness of the CoCr₂₀Pt₁₇ recording layer is increased to 11 nm,and wherein finer control of the % O₂ content was provided (by the meansdescribed above). As is evident from FIG. 3(B), when finercontrol/adjustement of the % O₂ content is provided, the critical % O₂content that creates the greatest effect (i.e., change) in nucleationfield (H_(n)) is seen to be much lower than that for the mediaillustrated in FIG. 3(A), i.e., about 0.10-0.20% O₂, e.g., ˜0.15% O₂.Kerr M-H hysteresis curves or loops for media samples with and withoutthe in situ post-deposition treatment of the magnetic recording layerwith oxygen gas at sub-atmospheric pressure are graphically shown inFIG. 4, from which it is apparent that the slope of the hysteresis curveor loop is increased, and H_(sat) and the switching field distribution(SFD) are decreased in media subjected to the in situ post-depositiontreatment of the magnetic recording layer.

[0090] FIGS. 5(A) and 5(B), respectively, graphically illustratesignal-to-media noise (SNR=SMNR) data (and thermal decay rates) fordual- and single-recording layer media with the following structure:substrate/adhesion layer: Ti (3 nm)/soft magnetic underlayer: FeCoB (200nm) interlayer(s): Ru (2 nm)/CoCr₃₇Pt₆ (7.5 nm), with the dual-recordinglayer design comprised of a first, CoCr₂₂Pt₁₉B₁ layer having a thicknessof 1 nm or 3 nm and a second, CoCr₂₀Pt₁₇ layer having a thickness of 9.5nm or 13.5 nm. The thickness of the CoCr₂₀Pt₁₇ layer of thesingle-recording layer media varied from 13-17 nm. The % O₂ content ofthe O₂/Ar gas mixture flowed past the surface of the magnetic recordinglayer(s) during the in situ post-deposition treatment was fixed at 0.05%and the treatment duration fixed at 3.5 sec. for all samples. Theobserved SNR is consistently greater for the samples subjected to the insitu post-deposition treatment. Thermal decay rates measured for 2samples at 75° C. are shown in FIG. 5(B) and indicate that the thermaldecay rate for the sample subjected to the in situ post-depositiontreatment (0.81%/decade) was lower than that of the sample not subjectedto the in situ post-deposition treatment (1.73%/decade).

[0091] While the mechanism for the benefits afforded by the in situpost-deposition oxygen treatment of the magnetic recording layer of theinstant invention is not clear, and not desirous of being bound by anyparticular theory, it is nonetheless observed that the increase in SMNR(or SNR) provided by the inventive post-treatment is correlated with thedecrease in switching field distribution (SFD), and the oxygenpost-treatment is believed to break up ill- or poorly-defined grains andmagnetic clusters, thereby resulting in the narrower SFD.

[0092] Extremely fine control of the magnetic properties of recordingmedia subjected to the inventive in situ oxygen post-treatment is madepossible by finer adjustment of the % O₂ content in the O₂/inert gasmixture using an O₂ source (e.g., gas cylinder) with a lower O₂ content.The variations of H_(c) and H_(n) as the % O₂ content varies from 0 toabout 0.1% for media having a 15 nm thick CoCt₂₀Pt₁₇ recording layer aregraphically shown in FIG. 6, and M-H hysteresis loops or curves for thesame media samples are shown in FIG. 7. As is evident from the latter,the shape of the M-H hysteresis loops or curves changed monotonically asthe % O₂ content increased from 0 to about 0.1%.

[0093] Although the precise % O₂ content necessary for effecting desiredchanges in the magnetic properties of the media depends upon thecomposition and thickness of the magnetic recording layer, the changesare more dependent upon the design of the media fabrication tool, e.g.,the design of the chamber utilized for performing the in situpost-deposition oxygen treatment. An example of such dependence upondesign of the post-treatment chamber is shown in FIG. 8, wherein thevariations in H_(c) and H_(n) as a function of % O₂ content in theO₂/inert carrier gas mixture are graphically presented. In thisinstance, both introduction and withdrawal of the gas mixture occurredvia the bottom of the post-treatment chamber. An increase in H_(n) wasagain observed when the % O₂ content was at least about 0.2%.

[0094] When the depth profiles of media samples utilized for developingthe graphs of FIGS. 3(A) and 3(B) were analyzed byTime-of-Flight/Secondary Ion Mass Spectroscopy (TEOS/SIMS), the presenceof chromium and cobalt oxides (CrO_(x) and CoO_(x)) was detected betweenthe carbon (C)-based protective overcoat layers and the recording layerswhen the % O₂ content of the O₂/inert carrier gas mixture was greaterthan about 0.1%. The amount of such chromium and cobalt oxides formedwhen the % O₂ content was less than about 0.1% was below the detectionlimit of the TEOS/SIMS technique. Therefore, depending upon the designof the media and the fabrication tool (e.g., post-treatment chamber),and selection of the analysis technique, oxide species formed as aresult of the inventive in situ post-deposition oxygen treatment may notbe detectable.

[0095] Perpendicular media with granular-type magnetic recordinglayers—A multi-chamber, single-disk type sputtering apparatus wasutilized for fabricating perpendicular-type magnetic recording mediacomprising granular-type magnetic recording layers, wherein the O₂/inertcarrier (diluent) gas mixture entered the dedicated in situpost-deposition treatment chamber via the top thereof and residual gaswas withdrawn via the bottom.

[0096] As indicated above such granular-type magnetic recording layerstypically comprise a CoPtX alloy, where X=at least one material selectedfrom the group consisting of Cr, Ta, B, Mo, V, Nb, W, Zr, Re, Ru, Cu,Ag, Hf, Ir, Y, SiO₂, SiO, Si₃N₄, Al₂O₃, AlN, TiO, TiO₂, TiO_(x), TiN,TiC, Ta₂O₃, NiO, and CoO, and wherein Co-containing grains with hcplattice structure are segregated by oxide, nitride, or carbide grainboundaries.

[0097] The following media structures were formed:

Substrate//adhesion layer: Ti//soft magnetic underlayer(s): FeCoB (50nm)/Ta (2.5 nm)/FeCoB (50 nm)//interlayer(s): Ag (1.5 nm)/Ru orRuCr₁₀//granular-type recording layer(s)//protective overcoat: C

[0098] The Ti adhesion layer and the Ta spacer layer between the pair ofFeCoB soft magnetic underlayers were sputtered in an Ar atmosphere atabout 6 mTorr pressure; the pair of FeCoB soft magnetic underlayers andthe Ag interlayer were sputtered in an Ar atmosphere at about 2 mTorrpressure; the RuCr₁₀ interlayer was sputtered in an Ar atmosphere atabout 12-35 mTorr pressure; and the granular-type recording layers werereactively sputtered in an Ar/O₂ atmosphere at a total pressure of about30-40 mTorr. The target compositions for the recording layers wereCoPt₁₈ and CoCr₆Pt₁₈(SiO₂)₄. Table II (below) presents the gas flowsutilized for each data point in FIGS. 9(A)-9(B) and 10(A)-10(B). TableIII (below) presents details of the process conditions for forming the(CoPt₁₈)O_(x) and CoCr₆Pt₁₈(SiO₂)₄O_(x) recording layers of the media ofFIGS. 9 and 10, respectively.

[0099] Deposition of each layer of the media samples was performed atambient temperature. In each case, the duration and total gas pressureof the inventive in situ post-deposition treatment with oxygen gas wereabout 3.5 sec. and about 20 mTorr, respectively. However, the in situpost-deposition treatment may be performed within intervals as short asabout 2 sec. and at total gas pressures of about 10-13 mTorr to obtainconsistent results. The % O₂ content in the O₂/Ar gas mixture iscontrolled by use of MFC 1 and MFC 2 TABLE II % O₂ Content in O₂/Ar 0 12 3 4 5 MFC 1: 100% Ar (sccm) 0 32 24 16 8 0 MFC 2: 5% O₂ in Ar (sccm) 08 16 24 32 40

[0100] TABLE III RuCr RuCr interlayer Granular layer Granular layerinterlayer sputtering comp. & sputtering thickness pressure thicknesspressure 16 nm 12 mTorr (CoPt₁₈)O_(x) 30 mTorr  9 nm 18 nm 25 mTorrCoCr₆Pt₁₈(SiO₂)₄O_(x) 38 mTorr 10 nm

[0101] FIGS. 9(A)-9(B) and 10(A)-10(B), respectively, graphicallyillustrate the variation of signal-to-noise ratio (SNR) and coercivity(H_(c))+nucleation field (H_(n)) of (CoPt₁₈)O_(x) granular-typeperpendicular magnetic recording media and CoCr₆Pt₁₈(SiO₂)₄O_(x)granular-type perpendicular magnetic recording media as a function of %oxygen content during in situ post-deposition oxidation treatment of themagnetic recording layer. As is apparent from FIGS. 9(A)-9(B), when the% O₂ content in the O₂/Ar gas mixture was varied from 0 to about 5%, theSNR of the media with the (CoPt₁₈)O_(x) granular-type perpendicularmagnetic recording layers improved by more than about 1 dB at an optimum% O₂ content of about 1%, and the values of H_(n) were higher than withmedia samples which were not subjected to the inventive in situpost-deposition oxygen gas treatment of the magnetic recording layer. Asfor the CoCr₆Pt₁₈(SiO₂)₄O_(x) granular-type perpendicular magneticrecording media illustrated in FIGS. 10(A)-10(B), while the changes inSNR and magnetic properties are not as large as those exhibited by the(CoPt₁₈)O_(x) granular-type perpendicular magnetic recording mediaillustrated in FIGS. 9(A)-9(B), the inventive in situ post-depositionoxygen gas treatment of the magnetic recording layer nonethelessresulted in consistent improvement in the SNR.

[0102] In summary, higher negative nucleation fields (−H_(n)) andresultant improved thermal stability of magnetic recording media can beobtained by subjecting the magnetic recording layer, as deposited, tothe inventive in situ post-deposition oxygen gas treatment, wherein themagnetic recording layer is exposed, at a sub-atmospheric pressure andfor a relatively short interval, to a small amount of O₂ gas admixedwith a larger amount of at least one inert carrier (diluent) gas, e.g.,Ar and/or N₂ prior to formation of the protective overcoat layerthereon. The relatively short duration of the in situ post-depositiontreatment process necessary for obtaining a desired improvement in theperformance characteristics of the media is fully compatible with theproduct throughput (e.g., cycle) requirements of automated apparatus forindustrial-scale manufacture of magnetic recording media, e.g., harddisks.

[0103] Finally, the inventive in situ post-deposition oxygen treatmenttechnique can be utilized with any type of magnetic recording media,regardless of the materials used for the substrate, adhesion layer, softmagnetic underlayer(s), interlayer(s), and recording layer(s). The % O₂content and process duration is preferably optimized according to themedia design and the fabrication tool (e.g., post-treatment chamber)utilized for the treatment to obtain the maximum benefit of theinventive methodology.

[0104] In the previous description, numerous specific details are setforth, such as specific materials, structures, processes, etc., in orderto provide a better understanding of the present invention. However, thepresent invention can be practiced without resorting to the detailsspecifically set forth. In other instances, well-known processingmaterials and techniques have not been described in detail in order notto unnecessarily obscure the present invention.

[0105] Only the preferred embodiments of the present invention and but afew examples of its versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is susceptibleof changes and/or modifications within the scope of the inventiveconcept as expressed herein.

What is claimed is:
 1. A method of manufacturing a magnetic recordingmedium, comprising sequential steps of: (a) providing an apparatus formanufacturing said medium; (b) supplying said apparatus with a substratefor said medium; (c) forming a magnetic recording layer on saidsubstrate in a first portion of said apparatus; (d) treating saidmagnetic recording layer with oxygen gas in a second portion of saidapparatus at a sub-atmospheric pressure and for an interval sufficientto provide the resultant medium with at least one of the following,relative to a similar medium manufactured by a similar method butwherein the oxygen treatment of step (d) is not performed: (i) a morenegative nucleation field (H_(n)); (ii) increased remanent squareness(S_(r)); (iii) increased signal-to-medium noise ratio (SMNR); (iv)narrower switching field distribution (SFD); and (v) decreased thermaldecay rate; and (e) forming a protective overcoat layer on saidoxygen-treated magnetic recording layer in a third portion of saidapparatus.
 2. The method according to claim 1, wherein: step (a)comprises providing an apparatus including at least said first, second,and third spaced-apart portions.
 3. The method according to claim 2,wherein: step (a) comprises providing an apparatus adapted forcontinuous manufacture of a plurality of media and including means fortransporting said substrate serially through said first, second, andthird spaced-apart portions.
 4. The method according to claim 3, whereinsaid first, second, and third spaced-apart, serially arranged portionsof said apparatus respectively comprise first, second, and thirdspaced-apart chambers and at least said second chamber is adapted forproviding a sub-atmospheric pressure therein.
 5. The method according toclaim 4, wherein said second chamber comprises means for flowing amixture of oxygen gas diluted with an inert carrier gas past a surfaceof said magnetic recording layer formed on said substrate in step (c).6. The method according claim 4, wherein said first and third chambersof said apparatus are adapted for performing a thin film depositionprocess therein.
 7. The method according to claim 6, wherein at leastsaid first chamber of said apparatus is adapted for performing asputtering process therein.
 8. The method according to claim 1, wherein:step (c) comprises forming a magnetic recording layer selected from thegroup consisting of: (1) a Co-based alloy, Cr-rich grain boundary typemagnetic layer; (2) a granular type magnetic layer; (3) asuperlattice-type layer; and (4) an L1₀ ferromagnetic metal alloy typelayer.
 9. The method according to claim 8, wherein: step (c) comprisesforming a Co-based alloy, Cr-rich grain boundary type magnetic recordinglayer comprised of a CoCrPtX alloy, where X=at least one elementselected from the group consisting of Ta, B, Mo, V, Nb, W, Zr, Re, Ru,Cu, Ag, Hf, Ir, and Y, and wherein Co-containing grains with hcp latticestructure are segregated by Cr-rich grain boundaries.
 10. The methodaccording to claim 9, wherein: step (d) comprises treating said magneticrecording layer with a gas mixture comprising up to about 20% oxygen gasin at least one inert diluent gas, at a total gas pressure up to about50 mTorr, and for an interval up to about 10 sec.
 11. The methodaccording to claim 10, wherein: step (c) further comprises utilizing aheated substrate during formation of said magnetic recording layer toeffect segregation of Cr in said grain boundaries.
 12. A perpendicularmagnetic recording medium manufactured by the method according to claim11.
 13. The method according to claim 8, wherein: step (c) comprisesforming a granular-type magnetic recording layer comprised of a CoPtXalloy, where X=at least one material selected from the group consistingof Cr, Ta, B, Mo, V, Nb, W, Zr, Re, Ru, Cu, Ag, Hf, Ir, Y, SiO₂, SiO,Si₃N₄, Al₂O₃, AlN, TiO, TiO₂, TiO_(x), TiN, TiC, Ta₂O₃, NiO, and CoO,and wherein Co-containing grains with hcp lattice structure aresegregated by oxide, nitride, or carbide grain boundaries.
 14. Themethod according to claim 13, wherein: step (d) comprises treating saidmagnetic recording layer with a gas mixture comprising up to about 20%oxygen gas in at least one inert diluent gas, at a total gas pressure upto about 50 mTorr, and for an interval up to about 10 sec.
 15. Themethod according to claim 14, wherein: step (d) comprises treating saidmagnetic recording layer with oxygen gas without applying heat thereto.16. A perpendicular magnetic recording medium manufactured by the methodaccording to claim
 15. 17. The method according to claim 8, wherein:step (c) comprises forming a superlattice-type magnetic recording layercomprising a multi-layer (CoX/Pd)_(n) or (CoX/Pt)_(n) structure, where nis an integer from about 10 to about 25 and X is an element selectedfrom the group consisting of Cr, Ta, B, Mo, Pt, W, and Fe; and step (d)comprises treating said magnetic recording layer with oxygen gas withoutapplying heat thereto.
 18. A perpendicular magnetic recording mediummanufactured by the method according to claim
 17. 19. The methodaccording to claim 8, wherein: step (c) comprises forming an L1₀ferromagnetic metal alloy-type layer comprising a FePt or CoPt alloy.20. A perpendicular magnetic recording medium manufactured by the methodaccording to claim
 19. 21. The method according to claim 1, wherein:step (b) comprises supplying said apparatus with a disk-shaped substratefor a hard disk magnetic recording medium.
 22. A disk drive comprising amagnetic recording medium formed by the process according to claim 21.23. The method according to claim 1, wherein: step (e) comprises forminga carbon-based protective overcoat layer on said oxygen-treated magneticrecording layer.
 24. A method of manufacturing magnetic recording mediaaccording to a continuous process, comprising sequential steps of: (a)providing at least one substrate for said magnetic recording media; (b)providing an apparatus adapted for continuous manufacturing of saidmagnetic recording media, comprising at least first, second, and thirdspaced-apart, serially arranged processing chambers and including meansfor transporting said at least one substrate serially through at leastsaid first, second, and third spaced-apart processing chambers; (c)transporting said substrate through said first processing chamber whileforming a magnetic recording layer thereon; (d) transporting saidsubstrate with said magnetic recording layer formed thereon to saidsecond processing chamber; (e) transporting said substrate through saidsecond processing chamber while treating said magnetic recording layerwith oxygen gas at a sub-atmospheric pressure and for an intervalsufficient to provide the resultant media with at least one of thefollowing, relative to similar media manufactured by a similar methodbut wherein the oxygen treatment of step (e) is not performed: (i) amore negative nucleation field (H_(n)); (ii) increased remanentsquareness (S_(r)); (iii) increased signal-to-medium noise ratio (SMNR);(iv) narrower switching field distribution (SFD); and (v) decreasedthermal decay rate; (f) transporting said substrate with saidoxygen-treated magnetic recording layer formed thereon to said thirdprocessing chamber; and (g) transporting said substrate through saidthird processing chamber while forming a protective overcoat layer onsaid oxygen-treated magnetic recording layer; wherein: said substrate istransported between and through each of said first, second, and thirdprocessing chambers at a substantially constant rate.
 25. The methodaccording to claim 24, wherein: step (a) comprises providing at leastone disk-shaped substrate for hard disk magnetic recording media; step(b) comprises providing an apparatus wherein said first and thirdchambers are adapted for performing a thin film deposition processtherein and at least said second chamber is adapted for providing asub-atmospheric pressure therein; and step (c) comprises forming amagnetic recording layer selected from the group consisting of: (1) aCo-based alloy, Cr-rich grain boundary type magnetic layer; (2) agranular type magnetic layer; (3) a superlattice-type layer; and (4) anL1₀ ferromagnetic metal alloy type layer.